Abstract Prenatal alcohol exposure (PAE) affects up to 5% of children in the United States, and is the topic of several NIH directives calling for research initiatives. Most children with PAE are diagnosed with ADHD, although current research demonstrates significant differences in symptom profiles and treatment response between ADHD due to PAE and idiopathic ADHD. This suggests corresponding clinically important differences in brain physiology between PAE ADHD and ADHD not associated with PAE (non-PAE ADHD). The research literature and our preliminary data demonstrate that aspects of executive function differentiate PAE ADHD from non- PAE ADHD. Further, in healthy and brain-injured subjects, metrics of executive function and attention have been correlated with fractional anisotropy (FA) in the anterior corona radiata (ACR) - a white-matter tract in which we found lower FA in children with PAE ADHD than in children with familial non-PAE ADHD. In the same group of children, using proton magnetic resonance spectroscopy (MRS), we also found lower levels of choline-compounds (Cho) in ACR in the children with PAE ADHD than in the children with familial non-PAE ADHD. Thus we propose that low FA and low Cho in ACR may provide objective neuroimaging markers to distinguish PAE ADHD from non-PAE ADHD. Fibers composing the ACR include those connecting the striatum and the anterior middle cingulate cortex (aMCC), a cingulate subregion heavily implicated in ADHD by functional neuroimaging. In our recent RC1, we found lower glutamate (Glu) in aMCC in children with familial ADHD (i.e., one or more siblings with ADHD, no PAE, and no family history of alcohol abuse) than in healthy controls. In PAE in contrast, pre-clinical literature suggests elevation of Glu in the cortex, along with reduction in gamma-aminobutyric acid (GABA). We propose that Glu/GABA ratios in aMCC may be an additional biomarker distinguishing PAE ADHD from familial non-PAE ADHD. In this investigation, we propose to use leading-edge MRS techniques (MRSI and MEGA-PRESS) in tandem with state-of-the-art diffusion tensor imaging (DTI) to test these brain imaging endpoints (FA and Cho in ACR, Glu/GABA in aMCC) that putatively differentiate PAE ADHD from familial non-PAE ADHD. We will furthermore explore relations between these endpoints and clinically relevant neurocognitive measures of attention and other executive functions. If successful, this proposal may inform the design of and the monitoring of in vivo effects of prospective treatments for PAE, which to date has been poorly tractable. This proposal responds to recommendations of the National Task Force on Fetal Alcohol Syndrome and Fetal Alcohol Effects to improve understanding of the mechanisms of alcohol's action on the brain through neuroimaging and to identify potential biomarkers of prenatal alcohol exposure and to the NIAAA Strategic Plan for Research which has identified ?developing increasing understanding of the effects of alcohol on neurodevelopment,? as a key public health goal.